The development of high-energy lasers, such as might be used in a military weapons system, has caused the need to accurately measure the characteristics of the beam. The characteristics to be measured are beam position, power distribution, and the variation of power distribution with time. The device herein disclosed, referred to as a "target board", is designed to make these measurements by making absolute power level measurements at discrete points over the area of the laser beam. The power level measurements are responsive to rapid changes in either intensity or position of the laser beam.